This invention relates generally to electrical switchgear and more particularly, to a method and apparatus for protecting, monitoring, and controlling the electrical switchgear.
In an industrial power distribution system, power generated by a power generation company may be supplied to an industrial or commercial facility wherein the power is distributed around the industrial or commercial facility to various equipment such as, for example, motors, welding machinery, computers, heaters, lighting, and other electrical equipment. At least some known power distribution systems include switchgear which facilitates dividing the power into branch circuits which supply power to various portions of the industrial facility. Circuit breakers are provided in each branch circuit to facilitate protecting equipment within the branch circuit. Additionally, circuit breakers in each branch circuit can facilitate minimizing equipment failures since specific loads may be energized or de-energized without affecting other loads, thus creating increased efficiencies, and reduced operating and manufacturing costs. Similar switchgear may also be used within an electric utility transmission system and a plurality of distribution substations, although the switching operations used may be more complex.
Switchgear typically includes multiple devices other than the power distribution system components to provide protection, monitoring, and control of the power distribution system components. For example, at least some known power distribution systems include a monitor device to monitor a performance of the power distribution system, a control device to control an operation of the power distribution system, and a protection device to initiate a protective response when the protection device is activated.
Further, at least some known power distribution systems include a monitor and control system which operates independently of a protective system. At least some known power distribution system includes a protective system capable of initiating a shutdown command for a portion of the power distribution system, which is not recorded by the monitoring system. For example, a protective device may shut down a portion of the power distribution system based on its own limits and the monitoring devices do not record the event. The failure of the monitoring system to record the system shutdown may cause an operator to believe that an over-current condition has not occurred within the power distribution system, and a proper corrective action therefore is not initiated by the operator. Additionally, a protective device, i.e. a circuit breaker, may open because of an over-current condition in the power distribution system, and the control system may interpret the over-current condition as a loss of power from the source power rather than a fault condition. Further, the control logic may attempt to connect the faulted circuit to an alternate source, thereby restoring the over-current condition, or the control logic may receive information that the protective device has opened due to an over-current condition and attempt to provide power to a load from an inactive circuit.
Accordingly, at least one known system includes a data capture system configured to capture current and/or voltage waveforms. The data capture system includes dedicated hardware and wiring. The use of multiple devices and interconnecting wiring associated with the devices may cause an increase in equipment size, an increase in the complexity of wiring the devices, an increase in a quantity of devices installed, and an increase in operational defects which may occur using the devices. Additionally, there is no practical, low cost way of capturing the system data and state, surrounding, i.e., before and after, trigger events, e.g., faults and alarms, for all circuit breakers in the system.